RESEARCH

Mechanical Properties of Soft Materials

Soft materials have gained attention in many research and industrial fields. For example, kinds of hydrogels have been developed to provide the mechanical environments favorable for culturing cells. Wearable or foldable electronic devices require conducting materials with an excellent flexibility. We characterize the mechanical properties of soft materials in terms of elasticity, plasticity, and viscosity using various techniques such as rheometry, AFM (Atomic Force Microscopy), nano-indentation, magnetic tweezers, and optical tweezers. Not only the properties of themselves but also interaction between soft materials are characterized in our group. Followings are soft materials of our interest.

Figure – Schematic of single molecular assay developed
using optical tweezers to probe the binding interaction
between actin filaments (green) and filamin (small red)
shown in the confocal image

Measurement Techniques for Biological Applications

We develop various measurement techniques to probe forces in biological specimens properly. Optical tweezers are used to generate a force in the order of pN which is relevant to force produced in single molecular events such as antibody-antigen binding and protein unfolding. Traction Force Microscopy (TFM) combined with the patterning technique is advantageous in studying the force generation for shaped-controlled cells. We are able to characterize mechanical properties of tissues using Atomic Force Microscopy (AFM) and rheometry.

Figure – Traction force microscopy and thin film assay
to measure forces for single cells and tissues

Biomimetics

Inspired by nature, we mimic structures and systems of living species at the multiscales. Highly ordered structures of cell are reconstituted in vitro by polymerizing cytoskeletal filaments at the environments where the mechanical, chemical or electrical conditions are similar to those in vivo. Tissue organization is replicated by culturing cells with specific patterns on a soft substrate with the physiologically-relevant stiffness. The principles learned from the biomimicry are applied to design engineering devices. Applications include an in vitro platform to test efficacy/toxicity of drugs, bio-inspired robots, and biosensors.

Figure – Shape-controlled single cells and tissue structures
of cardiac myocytes using the patterning technique

Mechanotransduction

Cells are able to produce, sense, and response to mechanical cues. Mechanotransduction refers to the mechanisms by which mechanical cues are converted into biochemical activities. We are specially interested in how mechanotransduction is altered in the state of diseases where the mechanical environments such as stiffness, boundary, and shape change significantly. Results of the studies are applied in understanding causes of diseases, developing new treatments, and constructing biomimetic tissue platform for drug tests.